The way that the Text Screen is set up is 80 characters wide and 25 characters high. Also, each character on the screen takes up two bytes of memory (therefore the 0..1). The first byte is the Character (such as 'A' '1' 'r' or whatever. The Second Byte is the color of that character. So if you use the [1] section of the array, you can change the Background/Foreground color of each character on the screen.

This byte is actually two nibbles (4-bits). The top 4-bits are the background color for the character and the lower 4-bits are the foreground color. So if you set [0,0,1] to Hex Number $17, The very top-left character on the screen will have a background that is Blue (1) and a foreground that is gray (7). *NOTE* If you set the background above color 7 (8-15) the character will flash on the screen.